Amine-Reactive and Photoreactive Crosslinkers

Although photoreactive aryl azides are relatively inert to thermochemical reactions prior to photolysis, they are not stable in the presence of sulfhydryl compounds which can reduce the 

Of the following amine-reactive and photoreactive crosslinkers, the overwhelming majority use an aryl azide group as the photosensitive functional group. Only a few use alternative photoreactive chemistries, particularly perfluorinated aryl azide, benzophenone, or diazo compounds. For general background information on photoreactive crosslinkers, see Das and Fox (1979), Kiehm and Ji (1977), Vanin and Ji (1981), and Brunner (1993). 

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Finally, the small amine-reactive and photoreactive crosslinker, NHS-ASA (Chapter 5, Section 3.1), can be iodinated to provide a non-cleavable radioactive conjugate. 

SADP, N-succinimidyl-(4-azidophenyl)l,3 -dithiopropionate, is a photoreactive heterobifunctional crosslinker that is cleavable by treatment with a disulfide reducing agent (Thermo Fisher). The crosslinker contains an amine-reactive NHS ester and a photoactivatable phenyl azide group, providing specific, directed coupling at one end and nonselective insertion capability at the other end. 

PNP-DTP, p-nitrophenyl-2-diazo-3,3,3-trifluoropropionate, is a photoreactive heterobifunctional crosslinker that contains an amine-reactive group on one end and a photosensitive diazo group on the other (Chowdhry et al., 1976) (Thermo Fisher), p-nitrophenyl esters react similarly... 

Figure 28.8 The heterobifunctional crosslinkers sulfo-SAND, SANPAH, and sulfo-SANPAH contain an amine-reactive (sulfo)NHS ester on one end and a photoreactive phenyl azide group on the other end. Sulfo-SAND allows release of conjugates by reduction of its internal disulfide bridge.

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